import _asyncio

@asyncio.coroutine
def hello():
    print("Hello world!")
    # 异步调用asyncio.sleep(1):
    r = yield from asyncio.sleep(1)
    print("Hello again!")

if __name__ == '__main__':
    # 获取EventLoop:
    loop = _asyncio.get_event_loop()
    # 执行coroutine
    loop.run_until_complete(hello())
    loop.close()
